A war, of sorts, is being waged on Buck Island just off St. Croix.
On one side in the battle is a countless horde of foreign invaders who have dug in deep amongst the island’s thickly shrubbed hills over the last century.
On the other is a relatively small contingent of specialists set on establishing a beachhead and then dislodging their foe, making the small Caribbean island safe for its residents and visitors alike.
Frank Boyd is the field marshal tasked with ridding the Buck Island Reef National Monument of the interlopers who are wreaking havoc on the island’s endangered and threatened flora and fauna. Although Boyd and his six comrades are ridiculously outnumbered, they have a secret weapon: peanut butter.
And it also helps that each of their foes has a brain, well, the size of a dried pea.
When Boyd and his team refer to the enemy forces as "dirty rats," it’s not a put-down; that's what they are. European black rats, or Rattus rattus, to be exact.
RAT RANGERS
"Rats are fairly predictable," Boyd says in his smooth Alabama drawl. "What makes them difficult to deal with is they’re so prolific."
The sheer number of rats on Buck Island has been a problem for years. The rodents were accidentally introduced to the West Indies on ships from Europe in colonial times. Without any natural predators, their numbers on Buck Island have grown to the point that they can devastate both plant and other animal populations.
It also means that anything is fair game, including endangered sea turtle eggs and hatchlings — or that unattended bologna sandwich.
The Buck Island rats have become "a problem to our visitors in the picnic areas," says Zandy Hillis-Starr, natural resource specialist for the National Park Service on St. Croix. But even worse, "their foraging activities are impacting ground nesting shorebirds, sea turtle nests and hatchlings and many small trees and shrubs."
With nearly 200 acres of rat-held territory to cover on the island, Boyd and his team of U.S. Department of Agriculture wildlife biologists and pest control specialists — a.k.a. the Rat Rangers — have a daunting task ahead of them. Their first job, and probably the easiest, was to map out a grid to cover the entire island.
With that done, the hard work began. Late last summer, armed with machetes and brush cutters, the Rat Rangers transferred the mapped-out grid to the actual island, complete with hills covered by poisonous manchineel trees, razor-spiked kasha bushes, cactus and the dreaded, rash-inducing Christmas bush. All under an unrelenting Caribbean sun.
The reason for this work was to cut a series of trail transects that would guide the placement of bait traps. Now there are 400 bait boxes, each resembling a little Hibachi grill, stuffed with irresistible -– if you’re a rat, anyway — peanut butter-laced poison positioned literally every 40 meters on Buck Island.
Every grid transect that fell on land is now the site of a bait station, Boyd says. "If you missed one spot, you could leave two rats. It’s an all or none thing."
KNOW THY ENEMY
To get an idea of what they were up against, the Rat Rangers did a little reconnaissance work. Before putting out the bait stations, they conducted snap-trap tests over three nights to gauge the density of the rodent population. The aim was to see how many rats went for the globs of peanut putter and oatmeal stuck on the traps.
Normally, Boyd says, if there aren’t too many, the numbers of rat casualties get smaller over the three nights. Not so on Buck Island.
"There were so many rats, we had to check the traps every hour," he says, "and the second night, we caught more. I could hear traps going off behind me after setting them. That’s generally not a good sign."
Knowing that they were vastly outnumbered, the Rat Rangers turned to their secret weapon –- small cubes of peanut butter poison. While the bait blocks are approved by the federal government for use around homes, Boyd says, they had never been used for battling rats on a project the scale of Buck Island.
For their proposed use on the island, the rangers needed a special registration from the U.S. Environmental Protection Agency. With that, the Rat Rangers keep data on every rat detail.
"We’ll want to use this data for future work in other areas," Boyd says, adding that the rats have to feed on the anti-coagulant poison several times before it kills, which means constantly checking the bait stations. "The low toxicity is for general safety," he says. "It makes for a little more work, but you have a safer technique."
Each day for 10 days the Rat Rangers don packs, heft buckets of bait and hump the hills of the island, checking each trap for signs of rat activity.
From the get-go, Boyd says, the Buck Island rats feasted on their new-found bait-box smorgasbords. Unlike their city cousins, the Caribbean rats didn’t show any signs of what Boyd calls "neophobia," or the fear of anything new.
"We haven’t seen that with these rats. They’re aggressive," he says. "You put something out there and they reach for it."
Simple it sounds, but miss a couple of rats and the whole process has to start again. That’s why Boyd, who has been dealing with a variety of problem critters for 20 years, doesn’t take his furry foes lightly.
"At about the time you think you know what they’re doing," he says, "they’re going to do just the opposite."
VICTORY?
With the bait boxes out at least 10 days, the Rat Rangers will do snap-trap tests in each quadrant of the island to see how effectively the poison worked. If a rat or rats end up in the traps, the area will be baited again, Boyd explains.
Follow-up tests will be done in June, then in late summer or fall the Rat Rangers will do a final test.
"Even one in a trap would mean we would have to start up [again] in that area," he says. "We’ll compare that data with the beginning. Hopefully, there will be no pattern."
He says "the most important aspect of a project like this is follow-up monitoring."
Another major strategy in the rat war will be the "pack-it-in, pack-it-out" tactic, Boyd says. That means visitors to Buck Island must assist in the effort to get rid of the rats by leaving no garbage behind when they leave.
"With garbage about, it would be hard for this project to be successful," he says. "Pack it in, pack it out. That alone will help rat control."
Contemplating his mission, Boyd concedes that rats aren’t as glamorous as, say, mountain lions, or other species that sometimes need to be controlled. The higher the order, he says, the more public controversy is involved.
"Everybody draws a line with trapping projects," he says. "From a biologist’s perspective they are all the same: You’re looking at population management. The public focuses on an individual species. Our job is to find a balance.
"The rats have conflicted with humans and turtles. And humans have placed a value on the turtles. But as a rule most people are really happy you’re getting rid of rats."
